In Euorpean Patent Specification No. 00 05 077, there is disclosed a so-called single-roller head which is used for the production of rubber or the like profiles. In such an arrangement, there is provided an extrusion unit, an extrusion head and a rotatable roller. In use, the extrusion unit, including the head, is moved under tension towards the roller. The head is in portions and a bearing plate is inserted between such portions and the roller. The bearing plate is made from a self-lubricating material such as molybdenum sulphide or polytetrafluoroethylene.
Such bearing plates have not, however, proved satisfactory in use. This is because the plate and the roller are not wear-resistant. The major disadvantage of such an arrangement is, however, that material can become lodged between the bearing plate and the surface of the roller. Such material is easily vulcanised and even burnt in this region due to the friction forces and the initial-tensioning pressure by means of which the bearing plate is pressed against the head. The burned residues cause the extruded profile or web to contain a high percentage of impurities and therefore to be useless.
An additional disadvantage of such single-roller head is that the entire head has to be removed if the mixture being extruded is changed and it is necessary to clear the head. Although the roller can be moved horizontally away from the head by means of spindles it is not possible to extract the screw from the extruder without first removing the head.